Emergence of invasive pneumococcal disease caused by multidrug-resistant serotype 19A among children in Barcelona

Abstract

Objective: To describe the epidemiology of invasive pneumococcal disease (IPD) caused by Streptococcus pneumoniae serotype 19A.

Methods: We studied all children and adolescents with IPD caused by serotype 19A who were admitted to a Children's Hospital in Barcelona (1997-2007). Serotyping, antibiotic susceptibility and clonal analysis were performed.

Results: Comparing the pre-vaccine period (1997-2001) with the early vaccine period (2002-2004) and the late vaccine period (2005-2007) there was an increase of IPD caused by serotype 19A: 1 of 58 episodes (1.7%) vs. 8 of 54 episodes (14.8%) vs. 27 of 123 episodes (21.9%), respectively (P = 0.002). All S. pneumoniae serotype 19A isolated in the pre-vaccine and early vaccine periods (n = 9) were penicillin susceptible, while in the late vaccine period, 12 of 27 (44%) were penicillin nonsusceptible (P = 0.01). A clonal analysis revealed 15 different sequence types (STs) expressing serotype 19A. 10 of them were preexisting STs associated with serotype 19A including the multidrug-resistant ST320 and ST276.

Conclusion: There was an increase of IPD caused by S. pneumoniae serotype 19A which was mainly related with the emergence of preexisting clones several of them closely related with international multidrug-resistant clones. These results should be considered when selecting the new conjugate pneumococcal vaccines.